A vehicle-to-vehicle communication system has been developed in which, at an intersection or the like of a poor visibility, a safe driving is supported by a wireless communication of information between vehicles. An infrastructure-to-vehicle communication system has been also developed in which a safe driving is supported by a wireless information communication from an infrastructure to a vehicle via a roadside unit. These wireless communications use radio waves, so that an available frequency band is allocated under a system by the Radio Law. Therefore, in the conventional technology, on the basis of the position and travel direction of the own vehicle, whether or not the vehicle comes into an area that restricts or prohibits the use of a specific frequency band is determined. When the own vehicle is determined to come into such an area, the transmission of radio waves is restricted or stopped (for example, Patent Literature 1).